How is it used?
The main use for LD is as a general indication of cell damage, including muscle damage, liver damage, blood cell damage and cancers. In the past, LD was used to help diagnose and monitor myocardial infarctions (heart attacks) but it has been replaced by a better test, troponin (more and to heart tissue injury than LD).
In people with progressive conditions, including melanoma, LD can be tested at regular intervals to monitor the progress of the condition.
When is it requested?
LD may be used as a screening test when some kind of cellular or tissue damage is suspected. If the LD is high other, more specific tests such as CK, ALT and AST can be used to help pinpoint the organs involved. Once the problem is diagnosed, LD levels may be tested at regular intervals to monitor its progress.
LD levels can also occasionally be ordered when someone has experienced muscle trauma or injury. They can also be ordered when someone has and of haemolytic anaemia.
LD testing may be ordered on a regular basis when someone has been diagnosed with cancer.
What does the test result mean?
High levels of LD usually indicate some type of tissue damage. Usually LD levels rise as the cell destruction begins, peak after some time and then begin to fall. As an example, when someone has a heart attack, blood levels of total LD rise within 24 to 48 hours, peak in two to three days and return to normal in 10 to 14 days.
Elevated levels of LD may be seen with:
With some chronic and progressive conditions, and some drugs, moderately elevated LD levels may persist.
Low levels of LD do not usually indicate a problem.
120 -250 U/L
The reference intervals shown above are known as a harmonised reference interval. This means that eventually all laboratories in Australia will eventually use this same interval so wherever your sample is tested, the reference interval should be the one shown above. Laboratories are in the process of adopting these harmonised intervals so it is possible that the intervals shown on the report of your results for this test may be slightly different until this change is fully adopted. More information can be found under Reference Intervals – An Overview
Is there anything else I should know?
Many things can affect LD results that are not necessarily a cause for concern. For example:
- Strenuous exercise can cause temporary elevations in LD
- Damage to the sample during and after collection can cause falsely elevated results by causing breakage of red blood cells in the sample (haemolysis)
- If the platelet count is increased, serum LD will be artificially high and not reflective of the LD actually present.